From patchwork Thu Jul 23 00:33:54 2020 Content-Type: text/plain; charset="utf-8" MIME-Version: 1.0 Content-Transfer-Encoding: 7bit X-Patchwork-Submitter: Serge Semin X-Patchwork-Id: 11679373 Return-Path: Received: from mail.kernel.org (pdx-korg-mail-1.web.codeaurora.org [172.30.200.123]) by pdx-korg-patchwork-2.web.codeaurora.org (Postfix) with ESMTP id 8EB5313B6 for ; Thu, 23 Jul 2020 00:35:44 +0000 (UTC) Received: from merlin.infradead.org (merlin.infradead.org [205.233.59.134]) (using TLSv1.2 with cipher ECDHE-RSA-AES256-GCM-SHA384 (256/256 bits)) (No client certificate requested) by mail.kernel.org (Postfix) with ESMTPS id 676A42071A for ; Thu, 23 Jul 2020 00:35:44 +0000 (UTC) Authentication-Results: mail.kernel.org; dkim=pass (2048-bit key) header.d=lists.infradead.org header.i=@lists.infradead.org header.b="bjb7NbKD" DMARC-Filter: OpenDMARC Filter v1.3.2 mail.kernel.org 676A42071A Authentication-Results: mail.kernel.org; dmarc=none (p=none dis=none) header.from=baikalelectronics.ru Authentication-Results: mail.kernel.org; spf=none smtp.mailfrom=linux-arm-kernel-bounces+patchwork-linux-arm=patchwork.kernel.org@lists.infradead.org DKIM-Signature: v=1; a=rsa-sha256; q=dns/txt; c=relaxed/relaxed; d=lists.infradead.org; s=merlin.20170209; h=Sender:Content-Transfer-Encoding: Content-Type:Cc:List-Subscribe:List-Help:List-Post:List-Archive: List-Unsubscribe:List-Id:MIME-Version:References:In-Reply-To:Message-ID:Date: Subject:To:From:Reply-To:Content-ID:Content-Description:Resent-Date: Resent-From:Resent-Sender:Resent-To:Resent-Cc:Resent-Message-ID:List-Owner; bh=vNYWpjgYx3RYSv0lR74Bm+hprF/U7hq+RHLixlW1U00=; b=bjb7NbKDrNW/x4vxJ4AtlpIiU LolFyitl62+lqpSF5GpMopWYbs6J+Pfje9fNuu2G/N6SIqYhX/ZTAqBDdxjFybS84EtkMwqv8Gais N5rHrCj2YBhcQAI8tNvr4AxpZuwLgXx/IDmK/ELqncxxNChWos1apc4Vi+p4GNnTBC25fR7TRHkZI 7FVrbj3ncyf+vzjuCDkIr3pSNAqDA1swFbmyW48m0bLp1J1+q5y9+db2QC6Iq5Bfb++yzYDYK87xN g7jc3gpVD0yKDnRQkgsmrLFKAllZXwJfx+eMc85O6t91So2XrEiyo9idJfEn7b0I4RnFXtlDalzD5 tTdX4t0cg==; Received: from localhost ([::1] helo=merlin.infradead.org) by merlin.infradead.org with esmtp (Exim 4.92.3 #3 (Red Hat Linux)) id 1jyPBl-0003Z6-Ty; Thu, 23 Jul 2020 00:34:22 +0000 Received: from mx.baikalelectronics.ru ([94.125.187.42] helo=mail.baikalelectronics.ru) by merlin.infradead.org with esmtp (Exim 4.92.3 #3 (Red Hat Linux)) id 1jyPBZ-0003Vv-3c for linux-arm-kernel@lists.infradead.org; Thu, 23 Jul 2020 00:34:11 +0000 Received: from localhost (unknown [127.0.0.1]) by mail.baikalelectronics.ru (Postfix) with ESMTP id CF1628040A68; Thu, 23 Jul 2020 00:34:00 +0000 (UTC) X-Virus-Scanned: amavisd-new at baikalelectronics.ru Received: from mail.baikalelectronics.ru ([127.0.0.1]) by localhost (mail.baikalelectronics.ru [127.0.0.1]) (amavisd-new, port 10024) with ESMTP id AXi9grj894nC; Thu, 23 Jul 2020 03:34:00 +0300 (MSK) From: Serge Semin To: Greg Kroah-Hartman , Jiri Slaby , Andy Shevchenko Subject: [PATCH v9 1/4] serial: 8250: Add 8250 port clock update method Date: Thu, 23 Jul 2020 03:33:54 +0300 Message-ID: <20200723003357.26897-2-Sergey.Semin@baikalelectronics.ru> In-Reply-To: <20200723003357.26897-1-Sergey.Semin@baikalelectronics.ru> References: <20200723003357.26897-1-Sergey.Semin@baikalelectronics.ru> MIME-Version: 1.0 X-ClientProxiedBy: MAIL.baikal.int (192.168.51.25) To mail (192.168.51.25) X-CRM114-Version: 20100106-BlameMichelson ( TRE 0.8.0 (BSD) ) MR-646709E3 X-CRM114-CacheID: sfid-20200722_203409_616607_A4EF1CF5 X-CRM114-Status: GOOD ( 14.60 ) X-Spam-Score: 0.0 (/) X-Spam-Report: SpamAssassin version 3.4.4 on merlin.infradead.org summary: Content analysis details: (0.0 points) pts rule name description ---- ---------------------- -------------------------------------------------- 0.0 SPF_HELO_NONE SPF: HELO does not publish an SPF Record -0.0 SPF_PASS SPF: sender matches SPF record X-BeenThere: linux-arm-kernel@lists.infradead.org X-Mailman-Version: 2.1.29 Precedence: list List-Id: List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , Cc: linux-kernel@vger.kernel.org, Russell King , Maxime Ripard , Alexey Malahov , Serge Semin , Andy Shevchenko , Pavel Parkhomenko , linux-serial@vger.kernel.org, Serge Semin , Will Deacon , linux-arm-kernel@lists.infradead.org Sender: "linux-arm-kernel" Errors-To: linux-arm-kernel-bounces+patchwork-linux-arm=patchwork.kernel.org@lists.infradead.org Some platforms can be designed in a way so the UART port reference clock might be asynchronously changed at some point. In Baikal-T1 SoC this may happen due to the reference clock being shared between two UART ports, on the Allwinner SoC the reference clock is derived from the CPU clock, so any CPU frequency change should get to be known/reflected by/in the UART controller as well. But it's not enough to just update the uart_port->uartclk field of the corresponding UART port, the 8250 controller reference clock divisor should be altered so to preserve current baud rate setting. All of these things is done in a coherent way by calling the serial8250_update_uartclk() method provided in this patch. Though note that it isn't supposed to be called from within the UART port callbacks because the locks using to the protect the UART port data are already taken in there. Signed-off-by: Serge Semin --- Changelog v4: - Export serial8250_update_uartclk() symbol for GPL modules only. Changelog v7: - Wake the device up on the serial port divider update. --- drivers/tty/serial/8250/8250_port.c | 40 +++++++++++++++++++++++++++++ include/linux/serial_8250.h | 2 ++ 2 files changed, 42 insertions(+) diff --git a/drivers/tty/serial/8250/8250_port.c b/drivers/tty/serial/8250/8250_port.c index 1632f7d25acc..f19757ef4999 100644 --- a/drivers/tty/serial/8250/8250_port.c +++ b/drivers/tty/serial/8250/8250_port.c @@ -2631,6 +2631,46 @@ static unsigned int serial8250_get_baud_rate(struct uart_port *port, (port->uartclk + tolerance) / 16); } +/* + * Note in order to avoid the tty port mutex deadlock don't use the next method + * within the uart port callbacks. Primarily it's supposed to be utilized to + * handle a sudden reference clock rate change. + */ +void serial8250_update_uartclk(struct uart_port *port, unsigned int uartclk) +{ + struct uart_8250_port *up = up_to_u8250p(port); + unsigned int baud, quot, frac = 0; + struct ktermios *termios; + unsigned long flags; + + mutex_lock(&port->state->port.mutex); + + if (port->uartclk == uartclk) + goto out_lock; + + port->uartclk = uartclk; + termios = &port->state->port.tty->termios; + + baud = serial8250_get_baud_rate(port, termios, NULL); + quot = serial8250_get_divisor(port, baud, &frac); + + serial8250_rpm_get(up); + spin_lock_irqsave(&port->lock, flags); + + uart_update_timeout(port, termios->c_cflag, baud); + + serial8250_set_divisor(port, baud, quot, frac); + serial_port_out(port, UART_LCR, up->lcr); + serial8250_out_MCR(up, UART_MCR_DTR | UART_MCR_RTS); + + spin_unlock_irqrestore(&port->lock, flags); + serial8250_rpm_put(up); + +out_lock: + mutex_unlock(&port->state->port.mutex); +} +EXPORT_SYMBOL_GPL(serial8250_update_uartclk); + void serial8250_do_set_termios(struct uart_port *port, struct ktermios *termios, struct ktermios *old) diff --git a/include/linux/serial_8250.h b/include/linux/serial_8250.h index 6545f8cfc8fa..2b70f736b091 100644 --- a/include/linux/serial_8250.h +++ b/include/linux/serial_8250.h @@ -155,6 +155,8 @@ extern int early_serial_setup(struct uart_port *port); extern int early_serial8250_setup(struct earlycon_device *device, const char *options); +extern void serial8250_update_uartclk(struct uart_port *port, + unsigned int uartclk); extern void serial8250_do_set_termios(struct uart_port *port, struct ktermios *termios, struct ktermios *old); extern void serial8250_do_set_ldisc(struct uart_port *port, From patchwork Thu Jul 23 00:33:55 2020 Content-Type: text/plain; charset="utf-8" MIME-Version: 1.0 Content-Transfer-Encoding: 7bit X-Patchwork-Submitter: Serge Semin X-Patchwork-Id: 11679375 Return-Path: Received: from mail.kernel.org (pdx-korg-mail-1.web.codeaurora.org [172.30.200.123]) by pdx-korg-patchwork-2.web.codeaurora.org (Postfix) with ESMTP id 385E517C5 for ; Thu, 23 Jul 2020 00:35:45 +0000 (UTC) Received: from merlin.infradead.org (merlin.infradead.org [205.233.59.134]) (using TLSv1.2 with cipher ECDHE-RSA-AES256-GCM-SHA384 (256/256 bits)) (No client certificate requested) by mail.kernel.org (Postfix) with ESMTPS id 120C12071A for ; Thu, 23 Jul 2020 00:35:45 +0000 (UTC) Authentication-Results: mail.kernel.org; dkim=pass (2048-bit key) header.d=lists.infradead.org header.i=@lists.infradead.org header.b="NN33L8Aa" DMARC-Filter: OpenDMARC Filter v1.3.2 mail.kernel.org 120C12071A Authentication-Results: mail.kernel.org; dmarc=none (p=none dis=none) header.from=baikalelectronics.ru Authentication-Results: mail.kernel.org; spf=none smtp.mailfrom=linux-arm-kernel-bounces+patchwork-linux-arm=patchwork.kernel.org@lists.infradead.org DKIM-Signature: v=1; a=rsa-sha256; q=dns/txt; c=relaxed/relaxed; d=lists.infradead.org; s=merlin.20170209; h=Sender:Content-Transfer-Encoding: Content-Type:Cc:List-Subscribe:List-Help:List-Post:List-Archive: List-Unsubscribe:List-Id:MIME-Version:References:In-Reply-To:Message-ID:Date: Subject:To:From:Reply-To:Content-ID:Content-Description:Resent-Date: Resent-From:Resent-Sender:Resent-To:Resent-Cc:Resent-Message-ID:List-Owner; bh=fHbwmv4DPeHZgM9UeFvh88gVcS4d+yf4kLEqw0nVU1E=; b=NN33L8Aankov3XeMtS+3i4xMK 6PQwoxB/cejV7LO5O2ExfbgSnr0t2DtKmSm2WpEwD1O1fsUWO/ejQw+IjijEGETwyDdHcWtv8ybNV FW5iQYlzZXys4RaP1hh+SlnCXoW6STkwaEpOnL7LUWk5rMMQQeDCi/eLVclVweGNuZE3OtRHjDsKl k8BgHxZcEmsvwKUdo+0G8dEqFrzQL5bg1OogCzYDpF3uoJc4rln57Ux9MAwcCDu3nSKntknwxVavj 9ttpjmTJ/BZ6i+C7dvea26arOKWxYHcx3KCvl+dcTVKRGrXkX1adOpA3xi4c6ifTplmyrHohvKEv7 eH+JZWcuA==; Received: from localhost ([::1] helo=merlin.infradead.org) by merlin.infradead.org with esmtp (Exim 4.92.3 #3 (Red Hat Linux)) id 1jyPBc-0003Xi-EU; Thu, 23 Jul 2020 00:34:12 +0000 Received: from ns2.chip.baikal.ru ([94.125.187.42] helo=mail.baikalelectronics.ru) by merlin.infradead.org with esmtp (Exim 4.92.3 #3 (Red Hat Linux)) id 1jyPBZ-0003Vy-2X for linux-arm-kernel@lists.infradead.org; Thu, 23 Jul 2020 00:34:10 +0000 Received: from localhost (unknown [127.0.0.1]) by mail.baikalelectronics.ru (Postfix) with ESMTP id 6AB198030816; Thu, 23 Jul 2020 00:34:01 +0000 (UTC) X-Virus-Scanned: amavisd-new at baikalelectronics.ru Received: from mail.baikalelectronics.ru ([127.0.0.1]) by localhost (mail.baikalelectronics.ru [127.0.0.1]) (amavisd-new, port 10024) with ESMTP id jJq91sKe2DEP; Thu, 23 Jul 2020 03:34:00 +0300 (MSK) From: Serge Semin To: Greg Kroah-Hartman , Jiri Slaby , Andy Shevchenko Subject: [PATCH v9 2/4] serial: 8250_dw: Simplify the ref clock rate setting procedure Date: Thu, 23 Jul 2020 03:33:55 +0300 Message-ID: <20200723003357.26897-3-Sergey.Semin@baikalelectronics.ru> In-Reply-To: <20200723003357.26897-1-Sergey.Semin@baikalelectronics.ru> References: <20200723003357.26897-1-Sergey.Semin@baikalelectronics.ru> MIME-Version: 1.0 X-ClientProxiedBy: MAIL.baikal.int (192.168.51.25) To mail (192.168.51.25) X-CRM114-Version: 20100106-BlameMichelson ( TRE 0.8.0 (BSD) ) MR-646709E3 X-CRM114-CacheID: sfid-20200722_203409_441746_BE1A158A X-CRM114-Status: UNSURE ( 9.66 ) X-CRM114-Notice: Please train this message. X-Spam-Score: 0.0 (/) X-Spam-Report: SpamAssassin version 3.4.4 on merlin.infradead.org summary: Content analysis details: (0.0 points) pts rule name description ---- ---------------------- -------------------------------------------------- 0.0 SPF_HELO_NONE SPF: HELO does not publish an SPF Record -0.0 SPF_PASS SPF: sender matches SPF record X-BeenThere: linux-arm-kernel@lists.infradead.org X-Mailman-Version: 2.1.29 Precedence: list List-Id: List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , Cc: linux-kernel@vger.kernel.org, Russell King , Maxime Ripard , Alexey Malahov , Serge Semin , Andy Shevchenko , Pavel Parkhomenko , linux-serial@vger.kernel.org, Serge Semin , Will Deacon , linux-arm-kernel@lists.infradead.org Sender: "linux-arm-kernel" Errors-To: linux-arm-kernel-bounces+patchwork-linux-arm=patchwork.kernel.org@lists.infradead.org Really instead of twice checking the clk_round_rate() return value we could do it once, and if it isn't error the clock rate can be changed. By doing so we decrease a number of ret-value tests and remove a weird goto-based construction implemented in the dw8250_set_termios() method. Signed-off-by: Serge Semin --- Changelog v3: - This is a new patch. --- drivers/tty/serial/8250/8250_dw.c | 15 ++++----------- 1 file changed, 4 insertions(+), 11 deletions(-) diff --git a/drivers/tty/serial/8250/8250_dw.c b/drivers/tty/serial/8250/8250_dw.c index aab3cccc6789..12866083731d 100644 --- a/drivers/tty/serial/8250/8250_dw.c +++ b/drivers/tty/serial/8250/8250_dw.c @@ -282,20 +282,13 @@ static void dw8250_set_termios(struct uart_port *p, struct ktermios *termios, clk_disable_unprepare(d->clk); rate = clk_round_rate(d->clk, baud * 16); - if (rate < 0) - ret = rate; - else if (rate == 0) - ret = -ENOENT; - else + if (rate > 0) { ret = clk_set_rate(d->clk, rate); + if (!ret) + p->uartclk = rate; + } clk_prepare_enable(d->clk); - if (ret) - goto out; - - p->uartclk = rate; - -out: p->status &= ~UPSTAT_AUTOCTS; if (termios->c_cflag & CRTSCTS) p->status |= UPSTAT_AUTOCTS; From patchwork Thu Jul 23 00:33:56 2020 Content-Type: text/plain; charset="utf-8" MIME-Version: 1.0 Content-Transfer-Encoding: 7bit X-Patchwork-Submitter: Serge Semin X-Patchwork-Id: 11679369 Return-Path: Received: from mail.kernel.org (pdx-korg-mail-1.web.codeaurora.org [172.30.200.123]) by pdx-korg-patchwork-2.web.codeaurora.org (Postfix) with ESMTP id BA42E13B6 for ; Thu, 23 Jul 2020 00:35:36 +0000 (UTC) Received: from merlin.infradead.org (merlin.infradead.org [205.233.59.134]) (using TLSv1.2 with cipher ECDHE-RSA-AES256-GCM-SHA384 (256/256 bits)) (No client certificate requested) by mail.kernel.org (Postfix) with ESMTPS id 929F520656 for ; Thu, 23 Jul 2020 00:35:36 +0000 (UTC) Authentication-Results: mail.kernel.org; dkim=pass (2048-bit key) header.d=lists.infradead.org header.i=@lists.infradead.org header.b="x9xJaqxu" DMARC-Filter: OpenDMARC Filter v1.3.2 mail.kernel.org 929F520656 Authentication-Results: mail.kernel.org; dmarc=none (p=none dis=none) header.from=baikalelectronics.ru Authentication-Results: mail.kernel.org; spf=none smtp.mailfrom=linux-arm-kernel-bounces+patchwork-linux-arm=patchwork.kernel.org@lists.infradead.org DKIM-Signature: v=1; a=rsa-sha256; q=dns/txt; c=relaxed/relaxed; d=lists.infradead.org; s=merlin.20170209; h=Sender:Content-Transfer-Encoding: Content-Type:Cc:List-Subscribe:List-Help:List-Post:List-Archive: List-Unsubscribe:List-Id:MIME-Version:References:In-Reply-To:Message-ID:Date: Subject:To:From:Reply-To:Content-ID:Content-Description:Resent-Date: Resent-From:Resent-Sender:Resent-To:Resent-Cc:Resent-Message-ID:List-Owner; bh=NUma5YDaAVVg25aKpiU0ShZPJqYHpd9d6L6sELa4Ab4=; b=x9xJaqxusIV4qF2l0dH+u2XFf YMIUelOEJGNCxRqz4FhhqgmhilPFlx7BA/Yes1r/o7rXyOToDQ15rTuFl++6oAHuMktwrkNl2Hq0M W5bNsGY6o0YEt9svl0ZiYpSG4FnbNDqJV/MV56rYGG4AgCol4NLFOyHltzuZ1KP+1+AvmhMOEsBwA VtKy9RXKWgtEwZzuPlefIvp18K1WWhG+jy1figFEz30ipOyQL57sYGOBBuU9WJ4sXEp/k/bPPbDL0 7u02QJqJH0VbCm8N0bLwYZlAMJhFhPqfPJrNj+G6xOLKp//hxziONtfvkRx+aQTlKwL6MdLWeCRua nMdX+i+vA==; Received: from localhost ([::1] helo=merlin.infradead.org) by merlin.infradead.org with esmtp (Exim 4.92.3 #3 (Red Hat Linux)) id 1jyPBe-0003YL-28; Thu, 23 Jul 2020 00:34:14 +0000 Received: from mx.baikalchip.com ([94.125.187.42] helo=mail.baikalelectronics.ru) by merlin.infradead.org with esmtp (Exim 4.92.3 #3 (Red Hat Linux)) id 1jyPBZ-0003W2-2y for linux-arm-kernel@lists.infradead.org; Thu, 23 Jul 2020 00:34:10 +0000 Received: from localhost (unknown [127.0.0.1]) by mail.baikalelectronics.ru (Postfix) with ESMTP id D7DB680045E5; Thu, 23 Jul 2020 00:34:02 +0000 (UTC) X-Virus-Scanned: amavisd-new at baikalelectronics.ru Received: from mail.baikalelectronics.ru ([127.0.0.1]) by localhost (mail.baikalelectronics.ru [127.0.0.1]) (amavisd-new, port 10024) with ESMTP id BfoAzdl2_QzI; Thu, 23 Jul 2020 03:34:01 +0300 (MSK) From: Serge Semin To: Greg Kroah-Hartman , Jiri Slaby , Andy Shevchenko Subject: [PATCH v9 3/4] serial: 8250_dw: Pass the same rate to the clk round and set rate methods Date: Thu, 23 Jul 2020 03:33:56 +0300 Message-ID: <20200723003357.26897-4-Sergey.Semin@baikalelectronics.ru> In-Reply-To: <20200723003357.26897-1-Sergey.Semin@baikalelectronics.ru> References: <20200723003357.26897-1-Sergey.Semin@baikalelectronics.ru> MIME-Version: 1.0 X-ClientProxiedBy: MAIL.baikal.int (192.168.51.25) To mail (192.168.51.25) X-CRM114-Version: 20100106-BlameMichelson ( TRE 0.8.0 (BSD) ) MR-646709E3 X-CRM114-CacheID: sfid-20200722_203409_386754_04DAF6E6 X-CRM114-Status: UNSURE ( 8.50 ) X-CRM114-Notice: Please train this message. X-Spam-Score: 0.0 (/) X-Spam-Report: SpamAssassin version 3.4.4 on merlin.infradead.org summary: Content analysis details: (0.0 points) pts rule name description ---- ---------------------- -------------------------------------------------- 0.0 SPF_HELO_NONE SPF: HELO does not publish an SPF Record -0.0 SPF_PASS SPF: sender matches SPF record X-BeenThere: linux-arm-kernel@lists.infradead.org X-Mailman-Version: 2.1.29 Precedence: list List-Id: List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , Cc: linux-kernel@vger.kernel.org, Russell King , Maxime Ripard , Alexey Malahov , Serge Semin , Andy Shevchenko , Pavel Parkhomenko , linux-serial@vger.kernel.org, Serge Semin , Will Deacon , linux-arm-kernel@lists.infradead.org Sender: "linux-arm-kernel" Errors-To: linux-arm-kernel-bounces+patchwork-linux-arm=patchwork.kernel.org@lists.infradead.org Indeed according to the clk API if clk_round_rate() has successfully accepted a rate, then in order setup the clock with value returned by the clk_round_rate() the clk_set_rate() method must be called with the original rate value. Suggested-by: Russell King Signed-off-by: Serge Semin --- Changelog v8: - This is a new patch created by the Russell King suggestion. --- drivers/tty/serial/8250/8250_dw.c | 6 +++--- 1 file changed, 3 insertions(+), 3 deletions(-) diff --git a/drivers/tty/serial/8250/8250_dw.c b/drivers/tty/serial/8250/8250_dw.c index 12866083731d..c1511f9244bb 100644 --- a/drivers/tty/serial/8250/8250_dw.c +++ b/drivers/tty/serial/8250/8250_dw.c @@ -275,15 +275,15 @@ dw8250_do_pm(struct uart_port *port, unsigned int state, unsigned int old) static void dw8250_set_termios(struct uart_port *p, struct ktermios *termios, struct ktermios *old) { - unsigned int baud = tty_termios_baud_rate(termios); + unsigned long newrate = tty_termios_baud_rate(termios) * 16; struct dw8250_data *d = to_dw8250_data(p->private_data); long rate; int ret; clk_disable_unprepare(d->clk); - rate = clk_round_rate(d->clk, baud * 16); + rate = clk_round_rate(d->clk, newrate); if (rate > 0) { - ret = clk_set_rate(d->clk, rate); + ret = clk_set_rate(d->clk, newrate); if (!ret) p->uartclk = rate; } From patchwork Thu Jul 23 00:33:57 2020 Content-Type: text/plain; charset="utf-8" MIME-Version: 1.0 Content-Transfer-Encoding: 7bit X-Patchwork-Submitter: Serge Semin X-Patchwork-Id: 11679377 Return-Path: Received: from mail.kernel.org (pdx-korg-mail-1.web.codeaurora.org [172.30.200.123]) by pdx-korg-patchwork-2.web.codeaurora.org (Postfix) with ESMTP id 6436117C7 for ; Thu, 23 Jul 2020 00:35:45 +0000 (UTC) Received: from merlin.infradead.org (merlin.infradead.org [205.233.59.134]) (using TLSv1.2 with cipher ECDHE-RSA-AES256-GCM-SHA384 (256/256 bits)) (No client certificate requested) by mail.kernel.org (Postfix) with ESMTPS id 3DCE92071A for ; Thu, 23 Jul 2020 00:35:45 +0000 (UTC) Authentication-Results: mail.kernel.org; dkim=pass (2048-bit key) header.d=lists.infradead.org header.i=@lists.infradead.org header.b="eJ31ILYj" DMARC-Filter: OpenDMARC Filter v1.3.2 mail.kernel.org 3DCE92071A Authentication-Results: mail.kernel.org; dmarc=none (p=none dis=none) header.from=baikalelectronics.ru Authentication-Results: mail.kernel.org; spf=none smtp.mailfrom=linux-arm-kernel-bounces+patchwork-linux-arm=patchwork.kernel.org@lists.infradead.org DKIM-Signature: v=1; a=rsa-sha256; q=dns/txt; c=relaxed/relaxed; d=lists.infradead.org; s=merlin.20170209; h=Sender:Content-Transfer-Encoding: Content-Type:Cc:List-Subscribe:List-Help:List-Post:List-Archive: List-Unsubscribe:List-Id:MIME-Version:References:In-Reply-To:Message-ID:Date: Subject:To:From:Reply-To:Content-ID:Content-Description:Resent-Date: Resent-From:Resent-Sender:Resent-To:Resent-Cc:Resent-Message-ID:List-Owner; bh=ANunUQG5FOlt/zLPVHryzAWlUQUFSpspCvKPG74jYzQ=; b=eJ31ILYjRJBrdajZnIYPhp9ni CIUtO9GAkdDFgPYFWkhB52/YqbLGqUsTx9x6A8PJCar/b9pYpeOOgf4W9b8RR1fFDE1clQ6vUj5ey MixG01p1tXoGJbM59t2ydsi7wL8kzbhaxtNxE4kEI3R49mwdSKTXdqXNZ9kZ9gWJxBpMKdzA2YWz9 7inDFlYpUi4IpNg8aBUxjfEDG6NIAs+YkINtMZoS6Abj98T7vVyOIBdKe6Qhw8wN7byLGLHrX5ist PGmLT6V5EXnnPPCQ6YX6DzNcheno14v7HKMJIk3S80nqYSePUH3BmZ3G6MMViFmD4wo1dC/V5v0S+ eiEfVnHrQ==; Received: from localhost ([::1] helo=merlin.infradead.org) by merlin.infradead.org with esmtp (Exim 4.92.3 #3 (Red Hat Linux)) id 1jyPBr-0003aB-1I; Thu, 23 Jul 2020 00:34:27 +0000 Received: from ns2.baikalchip.com ([94.125.187.42] helo=mail.baikalelectronics.ru) by merlin.infradead.org with esmtp (Exim 4.92.3 #3 (Red Hat Linux)) id 1jyPBZ-0003W7-1t for linux-arm-kernel@lists.infradead.org; Thu, 23 Jul 2020 00:34:11 +0000 Received: from localhost (unknown [127.0.0.1]) by mail.baikalelectronics.ru (Postfix) with ESMTP id 7A7F6803202F; Thu, 23 Jul 2020 00:34:03 +0000 (UTC) X-Virus-Scanned: amavisd-new at baikalelectronics.ru Received: from mail.baikalelectronics.ru ([127.0.0.1]) by localhost (mail.baikalelectronics.ru [127.0.0.1]) (amavisd-new, port 10024) with ESMTP id 3BovykwKELW8; Thu, 23 Jul 2020 03:34:01 +0300 (MSK) From: Serge Semin To: Greg Kroah-Hartman , Jiri Slaby , Andy Shevchenko Subject: [PATCH v9 4/4] serial: 8250_dw: Fix common clocks usage race condition Date: Thu, 23 Jul 2020 03:33:57 +0300 Message-ID: <20200723003357.26897-5-Sergey.Semin@baikalelectronics.ru> In-Reply-To: <20200723003357.26897-1-Sergey.Semin@baikalelectronics.ru> References: <20200723003357.26897-1-Sergey.Semin@baikalelectronics.ru> MIME-Version: 1.0 X-ClientProxiedBy: MAIL.baikal.int (192.168.51.25) To mail (192.168.51.25) X-CRM114-Version: 20100106-BlameMichelson ( TRE 0.8.0 (BSD) ) MR-646709E3 X-CRM114-CacheID: sfid-20200722_203409_599213_94E434C7 X-CRM114-Status: GOOD ( 28.87 ) X-Spam-Score: 0.0 (/) X-Spam-Report: SpamAssassin version 3.4.4 on merlin.infradead.org summary: Content analysis details: (0.0 points) pts rule name description ---- ---------------------- -------------------------------------------------- 0.0 SPF_HELO_NONE SPF: HELO does not publish an SPF Record -0.0 SPF_PASS SPF: sender matches SPF record X-BeenThere: linux-arm-kernel@lists.infradead.org X-Mailman-Version: 2.1.29 Precedence: list List-Id: List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , Cc: linux-kernel@vger.kernel.org, Russell King , Maxime Ripard , Alexey Malahov , Serge Semin , Andy Shevchenko , Pavel Parkhomenko , linux-serial@vger.kernel.org, Serge Semin , Will Deacon , linux-arm-kernel@lists.infradead.org Sender: "linux-arm-kernel" Errors-To: linux-arm-kernel-bounces+patchwork-linux-arm=patchwork.kernel.org@lists.infradead.org The race condition may happen if the UART reference clock is shared with some other device (on Baikal-T1 SoC it's another DW UART port). In this case if that device changes the clock rate while serial console is using it the DW 8250 UART port might not only end up with an invalid uartclk value saved, but may also experience a distorted output data since baud-clock could have been changed. In order to fix this lets at least try to adjust the 8250 port setting like UART clock rate in case if the reference clock rate change is discovered. The driver will call the new method to update 8250 UART port clock rate settings. It's done by means of the clock event notifier registered at the port startup and unregistered in the shutdown callback method. Note 1. In order to avoid deadlocks we had to execute the UART port update method in a dedicated deferred work. This is due to (in my opinion redundant) the clock update implemented in the dw8250_set_termios() method. Note 2. Before the ref clock is manually changed by the custom set_termios() function we swap the port uartclk value with new rate adjusted to be suitable for the requested baud. It is necessary in order to effectively disable a functionality of the ref clock events handler for the current UART port, since uartclk update will be done a bit further in the generic serial8250_do_set_termios() function. Signed-off-by: Serge Semin --- Changelog v2: - Move exclusive ref clock lock/unlock precudures to the 8250 port startup/shutdown methods. - The changelog message has also been slightly modified due to the alteration. - Remove Alexey' SoB tag. - Cc someone from ARM who might be concerned regarding this change. - Cc someone from Clocks Framework to get their comments on this patch. Changelog v3: - Refactor the original patch to adjust the UART port divisor instead of requesting an exclusive ref clock utilization. Changelog v5: - Refactor dw8250_clk_work_cb() function cheking the clk_get_rate() return value for being erroneous and exit if it is. - Don't update p->uartclk on the port startup. It will be updated later in the same procedure at the set_termios() function being invoked by the serial_core anyway. --- drivers/tty/serial/8250/8250_dw.c | 103 +++++++++++++++++++++++++++++- 1 file changed, 101 insertions(+), 2 deletions(-) diff --git a/drivers/tty/serial/8250/8250_dw.c b/drivers/tty/serial/8250/8250_dw.c index c1511f9244bb..87f450b7c177 100644 --- a/drivers/tty/serial/8250/8250_dw.c +++ b/drivers/tty/serial/8250/8250_dw.c @@ -19,6 +19,8 @@ #include #include #include +#include +#include #include #include #include @@ -43,6 +45,8 @@ struct dw8250_data { int msr_mask_off; struct clk *clk; struct clk *pclk; + struct notifier_block clk_notifier; + struct work_struct clk_work; struct reset_control *rst; unsigned int skip_autocfg:1; @@ -54,6 +58,16 @@ static inline struct dw8250_data *to_dw8250_data(struct dw8250_port_data *data) return container_of(data, struct dw8250_data, data); } +static inline struct dw8250_data *clk_to_dw8250_data(struct notifier_block *nb) +{ + return container_of(nb, struct dw8250_data, clk_notifier); +} + +static inline struct dw8250_data *work_to_dw8250_data(struct work_struct *work) +{ + return container_of(work, struct dw8250_data, clk_work); +} + static inline int dw8250_modify_msr(struct uart_port *p, int offset, int value) { struct dw8250_data *d = to_dw8250_data(p->private_data); @@ -260,6 +274,46 @@ static int dw8250_handle_irq(struct uart_port *p) return 0; } +static void dw8250_clk_work_cb(struct work_struct *work) +{ + struct dw8250_data *d = work_to_dw8250_data(work); + struct uart_8250_port *up; + unsigned long rate; + + rate = clk_get_rate(d->clk); + if (rate <= 0) + return; + + up = serial8250_get_port(d->data.line); + + serial8250_update_uartclk(&up->port, rate); +} + +static int dw8250_clk_notifier_cb(struct notifier_block *nb, + unsigned long event, void *data) +{ + struct dw8250_data *d = clk_to_dw8250_data(nb); + + /* + * We have no choice but to defer the uartclk update due to two + * deadlocks. First one is caused by a recursive mutex lock which + * happens when clk_set_rate() is called from dw8250_set_termios(). + * Second deadlock is more tricky and is caused by an inverted order of + * the clk and tty-port mutexes lock. It happens if clock rate change + * is requested asynchronously while set_termios() is executed between + * tty-port mutex lock and clk_set_rate() function invocation and + * vise-versa. Anyway if we didn't have the reference clock alteration + * in the dw8250_set_termios() method we wouldn't have needed this + * deferred event handling complication. + */ + if (event == POST_RATE_CHANGE) { + queue_work(system_unbound_wq, &d->clk_work); + return NOTIFY_OK; + } + + return NOTIFY_DONE; +} + static void dw8250_do_pm(struct uart_port *port, unsigned int state, unsigned int old) { @@ -283,9 +337,16 @@ static void dw8250_set_termios(struct uart_port *p, struct ktermios *termios, clk_disable_unprepare(d->clk); rate = clk_round_rate(d->clk, newrate); if (rate > 0) { + /* + * Premilinary set the uartclk to the new clock rate so the + * clock update event handler caused by the clk_set_rate() + * calling wouldn't actually update the UART divisor since + * we about to do this anyway. + */ + swap(p->uartclk, rate); ret = clk_set_rate(d->clk, newrate); - if (!ret) - p->uartclk = rate; + if (ret) + swap(p->uartclk, rate); } clk_prepare_enable(d->clk); @@ -312,6 +373,39 @@ static void dw8250_set_ldisc(struct uart_port *p, struct ktermios *termios) serial8250_do_set_ldisc(p, termios); } +static int dw8250_startup(struct uart_port *p) +{ + struct dw8250_data *d = to_dw8250_data(p->private_data); + int ret; + + /* + * Some platforms may provide a reference clock shared between several + * devices. In this case before using the serial port first we have to + * make sure that any clock state change is known to the UART port at + * least post factum. + */ + if (d->clk) { + ret = clk_notifier_register(d->clk, &d->clk_notifier); + if (ret) + dev_warn(p->dev, "Failed to set the clock notifier\n"); + } + + return serial8250_do_startup(p); +} + +static void dw8250_shutdown(struct uart_port *p) +{ + struct dw8250_data *d = to_dw8250_data(p->private_data); + + serial8250_do_shutdown(p); + + if (d->clk) { + clk_notifier_unregister(d->clk, &d->clk_notifier); + + flush_work(&d->clk_work); + } +} + /* * dw8250_fallback_dma_filter will prevent the UART from getting just any free * channel on platforms that have DMA engines, but don't have any channels @@ -407,6 +501,8 @@ static int dw8250_probe(struct platform_device *pdev) p->serial_out = dw8250_serial_out; p->set_ldisc = dw8250_set_ldisc; p->set_termios = dw8250_set_termios; + p->startup = dw8250_startup; + p->shutdown = dw8250_shutdown; p->membase = devm_ioremap(dev, regs->start, resource_size(regs)); if (!p->membase) @@ -468,6 +564,9 @@ static int dw8250_probe(struct platform_device *pdev) if (IS_ERR(data->clk)) return PTR_ERR(data->clk); + INIT_WORK(&data->clk_work, dw8250_clk_work_cb); + data->clk_notifier.notifier_call = dw8250_clk_notifier_cb; + err = clk_prepare_enable(data->clk); if (err) dev_warn(dev, "could not enable optional baudclk: %d\n", err);